3-227

TELCOM SEMICONDUCTOR, INC.

7

6

5

4

3

1

2

8

3-1/2 DIGIT

ANALOG-TO-DIGITAL CONVERTERS

TC7126

TC7126A

TYPICAL

GUARANTEED

MAXIMUM

TYPICAL

TYPICAL

200

180

160

140

120

100

80

60

40

20

0

TC7126A

ICL7136

NO

MAXIMUM

SPECIFIED

NO

MAXIMUM

SPECIFIED

ICL7126

Figure 8. TC7126A Internal Voltage Reference Connection

Figure 7. Analog Common Temperature Coefficient

APPLICATIONS INFORMATION

Liquid Crystal Display Sources

Several manufacturers supply standard LCDs to inter-

face with the TC7126A 3-1/2 digit analog-to-digital con-

verter.

Decimal Point and Annunciator Drive

The TEST pin is connected to the internally-generated

digital logic supply ground through a 500

Ω resistor. The

TEST pin may be used as the negative supply for external

CMOS gate segment drivers. LCD annunciators for decimal

points, low battery indication, or function indication may be

added without adding an additional supply. No more than 1

mA should be supplied by the TEST pin: its potential is

Flat Package

The TC7126A is available in an epoxy 64-pin formed-

lead flat package. A test socket for the TC7126ACBQ device

is available:

Part No.

IC 51-42

Manufacturer: Yamaichi

Distribution:

Nepenthe Distribution

2471 East Bayshore

Suite 520

Palo Alto, CA 94043

(415) 856-9332

Ratiometric Resistance Measurements

The TC7126A's true differential input and differential

reference make ratiometric readings possible. In ratiometric

operation, an unknown resistance is measured with respect

to a known standard resistance. No accurately-defined

reference voltage is needed.

The unknown resistance is put in series with a known

standard and a current passed through the pair. The voltage

developed across the unknown is applied to the input and

the voltage across the known resistor applied to the refer-

ence input. If the unknown equals the standard, the display

will read 1000. The displayed reading can be determined

from the following expression:

Displayed reading =

1000.

2

V

–

ANALOG

COMMON

TC7126A

VREF

+

32

35

36

26

240 k

Ω

10 k

Ω

VREF

–

VREF

1

+

9V

SET VREF = 1/2 VFULL SCALE

V

+

Representative

Manufacturer

Address/Phone

Crystaloid

5282 Hudson Dr.,

C5335, H5535,

Electronics

Hudson, OH 44236

T5135, SX440

216-655-2429

AND

720 Palomar Avenue

FE 0801,

Sunnyvale, CA 94086

FE 0203

408-523-8200

VGI, Inc.

1800 Vernon St., Ste. 2

I1048, I1126

Roseville, CA 95678

916-783-7878

Hamlin, Inc.

612 E. Lake St.,

3902, 3933, 3903

Lake Mills, WI 53551

414-648-2361